1. Field of Invention
This invention relates to clasps and closures and more particularly to single use fasteners having a head portion defining a slot at one end of an elongate strap that loops over and irremovably engages in the slot.
2. Background and Description of Prior Art
Fasteners of the instant type are commonly referred to as “cable ties” and are well-known for fastening items together such as container latches, bundles of wire and groupings of flexible tubular members. Typically the fastener is threaded through adjacent aligned holes defined in portions of a container that move distally from one another when the container is opened, or the fastener is extended circumferentially around the bundle of wires/groupings of hose to secure the wires/hoses in proximity to one another.
Generally, cable ties have an elongate strap that is tapered at one end portion. Opposite the tapered end portion is a dimensionally larger head portion defining a slot through which the tapered end portion of the elongate strap may be inserted. A resiliently displaceable pawl is carried within the slot and the pawl engages with one of a plurality of parallel adjacent transverse grooves defined in the elongate strap.
Cable tie type fasteners are typically single use items. Once the elongate strap is inserted through the slot and the pawl has engaged with the parallel transverse grooves, the elongate strap cannot be withdrawn from the slot without breaking the pawl, breaking the elongate strap or otherwise physically destroying the cable tie. Once the cable tie has been broken, it cannot be repaired or re-affixed.
The inability to remove a fastened cable tie without physically or functionally destroying the cable tie is both a desirable feature and a drawback.
Because of their single use nature, cable ties are commonly used in apparatus that require security, such as the transport of money, pharmaceuticals and other valuable commodities. When a container of the commodity is filled, closed and thereafter secured with a cable tie, it can reasonably be assumed that if the container, and in-place cable tie, are undisturbed when the container is later opened, and that the container and contents have not been tampered with. Conversely, if the container or the cable tie have been broken, it can reasonably be assumed that the original contents of the container have been tampered with and are no longer in the condition and perhaps quantity, as they were when the cable tie was originally secured to the container.
In the pharmaceutical industry, cable ties are used to securely close pharmaceutical tote boxes. A tote box arriving with the cable tie broken or damaged can be rejected or at a minimum closely inspected.
By the same token, one of the drawbacks of cable ties is that they are difficult to break. Cutting the cable tie with a wire cutter or knife poses a risk of unintentionally damaging the item being secured and requires use of a tool. Breaking the cable tie by inserting an elongate rigid object, such as a screwdriver, through the looped elongate strap and twisting the object to break the cable tie is even more likely to damage the item secured by the cable tie.
There are known “tear away” cable ties designed for easy removal. Tear away cable ties have a planar rectilinear tag adjacent the head portion and define a “scored” or “weakened” area between the tag and the head portion. Pulling on the rectilinear tag portion tears the cable tie at the “scored/weakened” area detaching the head portion from the strap portion without use of a tool or cutting device. Unfortunately, shearing forces such as those used to intentionally break known “tear away” cable ties may be inadvertently applied to the cable tie if the rectilinear tag is inadvertently caught between two surfaces that move relative to one another, such as a top and a bottom or adjacent sides of adjacent containers being transported in a vehicle. Any movement wherein one container moves along and across an adjacent container provides the necessary action to break known tear away cable ties. Further, known “tear away” cable ties with rectilinear tags have sharp edges and corners, they are not aesthetically pleasing, they are difficult to package in bundles because the rectilinear tags “catch” on one another and they can be difficult to manufacturer.
What is needed is a durable secure and tamper-proof cable tie type fastener that cannot be removed without destroying the cable tie, but can be intentionally removed without resorting to tools and without damaging the item being secured. The cable tie must be easy to use, not subject to unintentional breakage, aesthetically pleasing, easy to manufacture and package and must be able to be marked with unique identifying indicia.
Our twist off tamper-proof fastener addresses various of these drawbacks by providing a product that is strong and secure and is less likely to be inadvertently and unintentionally broken, but can also be broken without use of tools when desired. When broken, the fact the cable tie has been broken is un-mistakenly identifiable.
Our invention is an improved cable tie type fastener comprising an elongate strap of flexible yet strong plastic, preferably polypropylene, that defines a plurality of parallel adjacent transverse teeth in opposing planar surfaces. One end portion of the elongate strap is tapered to a rounded tip to ease insertion through a “T” slot defined in a head portion integrally carried at the end of the elongate strap opposite the tapered tip.
The “T” slot carries a fixed fingernail tooth and an opposing flexing arm having plural angular teeth that cooperatively engage with the transverse teeth defined in the elongate strap. The fingernail tooth and angulated teeth are configured to prevent the elongate strap from being withdrawn from the “T” slot once inserted therethrough and a peripheral frame around the “T” slot prevents insertion of tools that might be used to tamper with the flexing arm.
The head portion is elliptic having opposing spaced apart rounded end portions and opposing planar sides that can be marked with unique identification indicia, bar codes, trademarks and the like with lasers, ink jet printers and other known marking means to identify a particular cable tie, order or container to which the cable tie is affixed.
A circumferentially extending notch is formed in the elongate strap immediately adjacent the head portion. The notch does not negatively affect the axial or tensile strength of the cable tie.
The elliptic configuration of the head portion facilitates grasping and twisting of the head portion by a user. The twisting action focuses shearing forces on the elongate strap immediately below the head portion at the circumferentially extending notch. The twisting action breaks the cable tie at the circumferentially extending notch allowing the cable tie's removal without tools and without damaging the item to which the cable tie was fastened.